To artisans minimally skilled in wireless radio communication, it is well known that basic detection and subsequent location of a given continuously emitting wireless transmitter can be accomplished by merely connecting a radio receiver to one or more directional antennas and employing signal peaking methods. Such radio direction finding (“RDF”) techniques have been used successfully over many years to locate ships, planes, and individuals in distress. Single-receiver techniques sometimes employ null measurements to improve the final precision of directional measurements, but such null measurements rely on adequate carrier-to-interference ratios and may also be compromised by multiple reflected signals (“multipath”). Even with the best directional antennas, single-receiver radiolocation platforms may indicate signal peaks or nulls that turn out to be from reflecting surfaces rather than the desired transmitter itself. Single-receiver techniques at best indicate that one or more transmitted signals exist within a general area without precise boundaries, due in part to the inverse-square-law asymptotic RF signal propagation characteristic of radio waves in free space.
Two-receiver radiolocation platforms provide only modest improvement over single-receiver arrangements. Multipath reflected signals from continuously emitting transmitters can significantly contribute to directional measurement error, and signal-strength boundaries remain poorly defined. Additionally, use of relative time of arrival (“RTOA”) radiolocation techniques with only two synchronized receivers for locating digitally modulated RF transmitters will present nearly the same uncertainty as RDF directional measurements of continuously emitting RF transmitters. Two-receiver RTOA radiolocation platforms designed to locate such digitally modulated transmitters will, at best, predict which “disk” of circular area coordinates are possible for a given pair of RTOA values, with the disk being perpendicular to an imaginary line drawn between the two receivers, with the same poor definition of outer signal-strength boundaries.
Three-receiver synchronized radiolocation platforms with RTOA techniques for locating digitally modulated transmitters begin to offer the possibility of improved precision in both location and boundaries definition, in two dimensions only. The physical position of the three synchronized receivers defines the plane of the included two-dimensional area. Transmitters perpendicular to either side of the included two-dimensional plane will reintroduce increasing measurement error, with the same poor definition of outer signal-strength boundaries.
There are several group behavior sampling methods widely used in market research, traffic/crowd analysis and control, retail property management, and similar applications. Typical methods include various combinations of visible human observers, video systems, counting devices, portable scanners linked to a computer system, and similar technologies, to name a few. For group behavior sampling, most existing methods suffer from a relatively low sample rate, observation periods that may or may not coincide with periods of significant changes in behavior, the undesirable effect of the observer's presence influencing behavior in some way that contaminates measurement, and the scope being typically limited to one or just a few points of observation. Observation performed by an individual or a team can be “spotted” or out-maneuvered. Additionally, multiple observers face the challenge of coordinating observations to avoid duplication or other errors that could contaminate the accuracy, precision (or both) of the end result.
Current methods for tracking individuals suffer from many of the same limitations of typical methods used to sample group behavior in defined environments. Additionally, use of so-called intrusive “tracking” devices raises issues of permission, privacy intrusion and potential legal hurdles.
Secure access to buildings and other types of sensitive property typically requires physical keys/access cards that must be produced, distributed and recovered (or electronically disabled) from individuals. Unauthorized copies of keys and access cards can often be made without knowledge and permission of the issuing entity, and multiple levels of security with traditional secure access methods are often mutually exclusive. Taken together, such limitations can effectively obviate actual secure access and virtually always impose high administrative costs for what often turns out to be a relatively low level of actual security.
Certain businesses and other DLS facilities such as theaters, restaurants and churches have attempted to effect “quiet zone” environments by posting notices and/or verbally requesting customers or members to switch off or silence such terminal devices during their presence in the facility. Other facility operators have been reported to engage in the use of illegal “jamming” devices that effectively interdict all wireless terminal devices within facility premises. This method has the additional perverse effect of totally denying electronic access to certain exempt customers or members such as doctors or emergency services personnel, who may need to be instantly notified in the event of medical emergencies and threats to life or property. In this particular scenario, attempts at outgoing communication sessions would also be completely denied because the “jammed” wireless terminal would be unable to initially establish the required two-way session through the overhead “handshaking” protocol of the particular service. Absent some notice by the facility operator, interdiction by illegal jamming techniques would not likely be obvious to visitors with wireless terminals—the wireless terminal device would simply be non-functional without one's knowledge.
The limitations of present methods typically employed in sampling group behavior, tracking individuals, providing secure access, and controlling two-way wireless terminal alerts and operation are generally known by the operators of various DLSs and other entities. Certain methods, while extremely effective (i.e., “jamming”), have the distinct drawbacks of being illegal and/or denying electronic access to critical personnel without their knowledge. As such, a need exists for systems and methods to effectively and legally overcome such limitations in DLS environments. A particular need exists for systems and methods which overcome known limitations of certain applications and enable new services and features not anticipated by current wireless service delivery platforms or other approaches. To this end, systems and methods are desired which realize one or more of the following advantages: improved sampling precision; reduction of sampling inaccuracy; elimination of personal privacy intrusion; improved secure facility access at lower administrative cost; selective local control of two-way wireless terminal alerts and operation within the DLS; automatic control of DLS systems or subsystems such as security cameras; and remote control of systems and subsystems outside DLS boundaries.